Submarine signaling device covered with waterproof vibration damping shield



Jan. 31, 1950 WATERPROOF, VIBRATI AMPI Fil ed Aug. 1944 c. w; MELL ET AL SUBMARINE SIGNALING DEVICE COVERED WITH NG SHI ELD INVENTORJ.

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a 1 0 Wi/LL Patented Jan. 31, 1950 SUBMARINE SIGNALING DEVICE COVERED WITH WATERPROOF VIBRATION DAMP- ING SHIELD OFFI Clifford W. Mell' and Edwin C. Ballentine, Moorestown, N. J and James V. ONeill, Willow Grove, Pa., assignors to Radio Corporation of America, a corporation: of Delaware Application August 29, 1944, Serial No. 551,746

6' Claims. (Cl. 181-05) This invention relates to signal translating devices and more particularly to electro-acoustic transducers useful in underwater signal-ling.

Si nal translating devices of this type usually include a steel casing open at one end and closed oil at this end by a, vibratile diaphragm, the casing and diaphragm being generally both made of steel which is, of course, severely corroded by sea water. The diaphragm of such devices is usually arranged either to be driven by suitablesig'nalresponsive driving means, such as magnetostrictive driving elements, whereby it radiates compressional waves in the. water or other ambient, or to be driven by compressional waves in the ambient which are received by it for conversion into electrical signals. Now, it has been known that the casings of. such signalling devices or projectors are also subject to slight vibrations, andthis'results in a beam pattern which is very non-directional, producing a back wave which may be very troublesome at times.

Various types'of coatings; such as paint, lacquer, and the like, have been applied to the exterior surfaces of the casings and their diaphragms for the purposeof cuttin down corrosion; but these have not. been very efiective. Moreover, it has been found that branches and other forms of marine life accumulate and grow on such materials with considerable freedom, and this interitems with the proper: operation of theproj'ectors. In fact. after a period of use, conventional projectors usually'must be" withdrawn from-the water and thoroughly cleaned and repainted to render them suitable for use oncemore.

With respect to the troublesomeback waves, various proposals have been made tocover the projector casing with materials which are intendedtoattenuate the casing-vibrations. Among such materials arevarious grad'esof natural rub- 7 to provide an improved eleetro-acoustictransducer suitable forunderwater signalling which will be free from the aforem'enticm'ed difi'culti'es.

More particularly; it' is an object ofour-present inventionto'provide an improved underwater sound projector-which will'be free-from corrosion and other-attack-- by the" water; which will have good' coupling withthe water; andwhich -will' also have-a highly directional, beam=- pattern bothunder-trensmltting-and. receiving-conditions 2 provide an improved underwater sound projector which is characterized by a reduction of water noise in the receiving condition by red-ucng the noise pickup from the back and sides of the projector.

Still another object of our present invention is to provide an improved underwater sound projector which will permit signals to be received at relatively high speeds when it is mounted on a ship.

A further object of our present invention is to provide an improved underwater sound projector which has an increased range over similar projectors of the prior art.

Still a further object of our present invention is to provide an improved underwater sound projector which has a high sensitivity when used as a receiver.

Another object ofourpresent invention is to provide an improved coating for underwater sound projectors which will not onl eliminate corrosion, but which will also prevent the" accumulation and growth of barnacles' and the like on the projector casings.

It is also an object of our present invention to provide an improved co'at'i ng for underwater sound projectors which can be readily applied to existing projectors of this type and which will result in projectors having high effici'ency.

In accordance with our present invention, we provide on the casing and} diaphragm of the proj'ector a coating of synthetic rubber-1ike material capable of withstand ng the elements and of becoming readily wetted, and we include therewith, around the casing of" the projector, a material capable of attenuating the casing vibrations. The exterior metal surfaces of the projector casing and diaphragm are first chemically cleaned and then slightly etched; preferably by sand or steel blasting; A priming coat" for the rubberlike covering is then applied over'the projector. The diaphragm is then coated with a layer of about 01030 inch of neoprene or other suitable rubber-like synthetic material of similar character, the material being applied" by brushing; clipplug or spraying, as-may be found most suitable. On theback' and sides of the casing, we apply a mixture of ground cork and the synthetic rubher-like material. or: alayer of sheet cork isfirst applied directly to the casing; and then a coating of neoprene or thelike is applied to the'cork layer. The cork sheet'andthe final, outer coat of neoprene or" the like may each be approximately OL-OBOihch in: thickness. The aircellsiin Another object of our present-invention isto 55 'thecork, whethentl'lecorkis mixed with neoprene The novel features that we consider characteristic of our invention are set forth with particularity in the appended claims' The invention itself, however, both as to its organization and method of operation, as well as additional objects and advantages thereof, will best be understood from the following description of several embodiments thereof when read inconnection with the accompanying drawing, in which Figure 1 is a sectional view of an underwater sound projector according to one form of our invention,

Figure 2 is an enlarged, fragmentary, sectional view showing another form of our invention, and

Figure 3 is a similar, fragmentary view of still another form of our invention.

Referring in greater detail to the drawing, wherein similar reference characters designate corresponding parts throughout. there is shown, in Fig. 1, an underwater signalling device capa- .ble of use either as a projector or as a receiver of compressional waves and including a casing I of steel or the like having a normally open end closed by a vibratile diaphragm 2 of steel or other suitable magnetic material. The diaphragm 2 may be held in place on the casing I by a metal clamping ring 3 and a plurality of bolts 4. Within the casing I and secured to the diaphragm 2 are a plurality of magnetostrictive elements 5 each surrounded by a coil I. The elements 5 are adapted either to drive the diaphragm 2 upon being energized by signal currents passing through the coils I, whereby to generate compressional waves in the ambient, or to be driven by the diaphragm 2 in response to vibration of the diaphragm by compressional waves in the water or other ambient received by the diaphragm and thereby to set up signal currents in the coils 1. The construction thus far described is more .or less conventional and well known and therefore a further description thereof is not believed to be necessary.

Surrounding the casing I, the diaphragm 2, the clamping ring 3 and the, bolts 4 (in fact, all exposed metallic parts is a protective coating 9 according to one form of our invention. This coating may be constituted by any one or more .of the synthetic rubber-like materials which are ,now fairly well known and which we have found to have the requisite characteristic of being readily wetted by water. One material which we have found highly satisfactory is that known as neoprene, and it is applied by brushing, dipping.

spraying or the like in several coats. For this purpose, we have found that a solution of neoprene supplied by the Gates Engineering Company of 200 W. 9th St., Wilmington, Delaware is admirably suited.

The exposed surfaces of the casing I, the diaphragm 2, etc., are first chemically cleaned with solvents and alkaline cleaners in known manner, and they are then etched by acid or by sandor steel-blasting, the latter being preferred. primer coat (for example, a good rubber or latex cement) suitable for bonding neoprene or the like to the metal is then applied to the etched sur faces. Neoprene or the lik materialis apof approximately .010 inch, to provide a coat having a total thickness of about 0.030 inch. The combined coats are cured by heating in air for about 48 hours at approximately 200 F. Lower temperatures may be used but will require longer heating. In general, higher temperatures than 200 F. are not desirable due to the possibility of injuring certain of the projector parts. A protective coating of neoprene or the like applied as above is strong and durable; it provides excellent protection against corrosion or other attack by sea water or the elements; and it so inhibits the accumulation and growth of barnacles as to render the projector practically free from this difficulty. In addition, due to its ready wettability, it provides very good coupling between the projector and the water.

' Where it is desired to shield the back and the sides of the projector casing against back wave due to the slight vibration thereof, the casing I may-be covered with a coating 9a which is a mixture of cork particles and the neoprene or the like. The cork particles include a plurality of air cells I0 which act as the shielding medium. When cork alone is used, as has been proposed heretofore, the water is gradually soaked up by the cork and fills many of the air cells I!) as a result of which the efiectiveness of the cork as a damping medium is lost. However, when the cork particles are mixed with neoprene or similar synthetic rubber-like material, the cork is rendered waterproof and the air cells are retained. The mixture of cork and neoprene or the like is of pasty, putty-like consistency and may be applied by brushing or with a trowel. If desired, the layer 9a maybe covered with a layer of neoprene or similar material 9 by dipping the entire projector into a solution thereof when the diaphragm 2 and other parts are to be coated.

In place of the mixture of cork and neoprene, as in Fig. 2, the projector casing I may first be covered with a layer of sheet cork I I, as in Fig. 3,

and it may be bonded to the casing I by the purpose.

above mentioned primer coat or other suitable adhesive. A layer of neoprene or other suitable similar material 9 may then be applied over the cork layer I I. In the modifications of both Figs. 2 and 3, the cork itself is not of too great value in shielding the casing against back wave trans mission or reception, but it serves as a medium for holding the air cells In which accomplish this In place of the cork, any other suitable material capable of retaining air cells therein may be used, such as certain grades of paper, cardboard, fibre board, or such materials as Balsa .wood, or the like. In any case, the air cell retaining material is highly effective in attenuating the Vibrations of the casing, while the neoprene or similar coating is highly effective in preventing corrosion or other similar attack of the metal parts and in preventing the accumulation and growth of barnacles and other forms of marine life.

From the foregoing description, it will undoubtedly be apparent to those skilled in the art that ,we have provided an improved coating for underwater signalling devices which will not only prevent corrosion and deterioration thereof normal- 1y resulting from attack by the elements, but

which will afford excellent coupling between the projector and the water while at the same time attenuating vibration of the casing. Thus, we have provided a signalling device of thistype-in plied in several coats, preferably three coats each which the transmission and reception are greatly improved and more highly directional. Although we have shown and described our invention with particular reference to an underwater signalling device, we wish to point out that certain features thereof are also applicable to other wave energy converters. Thus, for example, neoprene or other similar rubber-like materials may be used as a covering for radio transmitting antennas, radar antennas, or other similar wave energy converters which are subject to corrosion and deterioration when exposed to the elements. Moreover, while we have shown and described several particular forms of our invention, it will undoubtedly be apparent to those skilled in the art that many other forms thereof, as well as variations in those described, are possible. We therefore desire that our invention shall not be limited except insofar as is made necessary by the prior art and by the spirit of the appended claims.

We claim as our invention:

1. An electroacoustical transducer including a casing and a vibratile diaphragm carried thereby, said casing and diaphragm both being subject to attack by the elements and said casing being normally also subject to slight vibration, and a protective coating on and totally enclosing said casing and diaphragm, said coating including a synthetic rubber-like material capable of withstanding the elements and having the characteristic of being wetted relatively easily, and at least an inner portion of said coating on said casing being cellular whereby it is adapted to attenuate the vibrations of said casing.

2. An electroacoustical transducer according to claim 1 wherein said synthetic rubber-like material is constituted by neoprene and wherein the thickness of said coating is of the order of 0.030 inch.

3. A submarine signalling device comprising a casing and a vibratile diaphragm carried thereby, said diaphragm being adapted to be driven either by signal forces to radiate wave energy in Water or by wave energy in the water received thereby to effect generation of signal forces and said casing being also normally subject to slight vibrations,

said casing and diaphragm being also subject to attack by the water, and a protective coating on and totally enclosing said casing and diaphragm, said coating including a rubber-like synthetic material capable of withstanding the water and havall 5. A submarine signalling device according to claim 3 wherein the inner layer of said coating on said casing is comprised of a mixture of said synthetic rubber-like material and cork particles, said mixture including said air cells.

6. A submarine signalling device comprising a casing and a vibratile diaphragm carried thereby, said diaphragm being adapted to be driven either by signal forces to radiate wave energy in water or by Wave energy in the water received thereby to efiect generation of signal forces and said casing being also normally subject to slight vibrations, said casing and diaphragm being also subject to attack by the water, and a protective coating on and totally enclosing said casing and diaphragm, said coating including an inner layer of cork about and secured to said casing only, said. cork layer having a plurality of air cells therein, and an outer continuous covering and layer of synthetic rubber-like material secured to said cork layer and to said diaphragm, said rubber-like material having the characteristic of being wetted relatively easily and being capable of withstanding the water to thereby protect said device from attack by the water and said cork layer about the casing serving to attenuate the vibration of said casing.

CLIFFORD W. MELL. EDWIN C. BALLENTINE. JAMES V. ONEIL-L.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 322,936 Hoyt July 28, 1885 772,676 Schiessler Oct. 18, 1904 1,345,717 Thomas July 6, 1920 1,624,412 Horton Apr. 12, 1927 1,632,331 Hayes June 14, 1927 1,873,578 Grupe Aug. 23, 1932 1,950,894 Koch Mar. 13, 1934 2,061,934 Mueller-Conradi Nov. 24, 1936 2,242,037 Levin May 13, 1941 2,257,932 Basler Oct. 7, 1941 2,310,629 Haarhoff Feb. 9, 1943 2,389,210 Pitman Nov. 20, 1945 FOREIGN PATENTS Number Country Date 844,452 France July 26, 1939 OTHER REFERENCES Neoprene Notebook No. 13, March 1939, pages 49 to 52, published at Wilmington, Del., by E. I. du Pont. 

